The present invention relates generally to sheet feeding apparatuses, and specifically to feed rollers and retard rollers with a wearable release outer layer and their use. It is further directed to a method testing these rollers and increasing the longevity of the rollers.
The present invention relates generally to scuff feeds for transporting sheets from a sheet stack, and more particularly, to a scuff feed having an outer layer that does not retain contaminants and wears slowly.
In modern reproduction apparatuses, such as electrostatographic copiers or printers, a latent image of information to be reproduced is formed on a uniformly charged dielectric member, altering the charge in an image-wise pattern. The latent image charge pattern is then developed with pigmented marking particles. Thereafter, the developed image is transferred to a receiver member and fixed to the receiver member by application of heat and/or pressure to form the desired reproduction.
In order to improve the productivity of reproduction apparatuses, sheet-feeding systems for reproduction devices have been developed. Several processes are known for separating sheets of paper to be loaded. Common feeding processes consist of using a combination of rollers that feed sheets of paper into the reproduction apparatus.
Paper separating mechanisms that use a friction retard systems include at least one paper feed roller and one retard member, which may be either a fixedly secured pad or a retard roller. Many apparatuses use the latter.
The two rollers form a nip between them that allows single sheets of paper to pass through. The retard roller uses a resistance mechanism to cause the roller to rotate at a predetermined rate. This rate is set so that exactly one sheet passes through the nip at a time. In the conventional paper separating mechanisms mentioned above, both the feed roller and the retard roller are made of rubber or similar material in order that these rollers may have appropriate coefficients of friction (COFs) relative to paper
The feed roller an the retard roller each comprise a core and an outer xe2x80x9ctire.xe2x80x9d The tire is a hollow cylindrical tube surrounding the core. The tires are placed around shafts that rotate. Sometimes an adhesive is used to hold the tire in place. During the feeding process a tire that is not secured may not rotate with the shaft. This will lead to either a nonfeed or double feed situation.
One problem with current feed and retard rollers is the short useful lifespan of many of them. It is desirable to use tire materials that have a long lifetime and a resistance to surface contamination. Many materials will absorb oils or pick up contaminants that may be on the substrate being fed into the reproduction apparatus. The oil and contaminants may decrease the lifetime of the roller. Contamination also decreases the COF of the roller, increasing the chances of the device not properly feeding sheets into the copier.
A second problem with current rollers is that the outer layer of feed rollers and the retard rollers usually have to be made out of different materials. This is undesirable since it also means different wear rates and different amounts of surface contamination.
An object of the invention was to create a sheet feeding apparatus that uses at least one feed roller having a much longer lifetime than current rollers.
A second object of the invention was to create a sheet feeding apparatus that uses at least one feed roller that resists contamination better than current feed rollers.
A third object of this invention is to demonstrate the proper way to choose the COF, nip pressure, and retard roller braking force, to achieve a maximum lifetime in systems that use a feed roller and a retard roller.
The invention is a sheet feeding apparatus comprising a feed roller and a retard roller. The rollers have an outer layer that is a material that wears at a rate sufficient to drastically reduce the amount of contaminants that collect on the feed roller.
The reduction in contaminants reduces the loss of COF of the rollers. The new improved rollers operate for much longer periods without misfeeds. Experimental evidence has demonstrated lifetimes of up to four times that of previous surface materials.
The present invention also includes novel ways of testing the new rollers as traditional testing methods were deemed inadequate, especially with regard to the wear rate and COF of the rollers.
The present invention also shows a method of exploiting a relationship among the COF, the nip pressure, and the retard roller braking force.